Nondazzling headlight for automobiles and the like



Nov. 15, 1932. D. BERG ,57

NONDAZZLING HEADLIGHT FOR AUTOMOBILES AND THE LIKE Filed Jan. 30, 1932 4 Sheets-Sheet 1 NOV. 15, 1932. BERG 1,887,574

NONDAZZLING HEADLIGHT FOR AUTOMOBILES AND THE LIKE Filed' Jan. 30, 1932 4 Sheets-Sheet 2 Nov. 15, 1932. D. BERG 1,887,574

NONDAZZLING HEADLIGHT FOR AUTOMOBILES AND THE LIKE Filed Jan. 30; 1932 4 Sheets-Sheet 3 D. BERG Nov. 15, 1932.

NONDAZZLING HEADLIGHT FOR AUTOMOBILES AND THE LIKE Filed Jan. 30, 1932 4 Sheets-Shee t 4 Patented Nov. 15, 1932 UNITED STATES;

PATE T oFFIcE'lf QDI'ILEV, mine, or HELLERUP, NEAR, COPENHAGEN, DENMARK NONDAZZLING HEADLIGHT FOR AUTOMOBILES AND THE IJIKE Application filed January 30, 1932, Serial No. 589,944,.and 1a Denmark January 30,1931.

It is'well known that the automobile head lights now in use are unsatisfactory, and, at times dangerous to use as they emit rays'having frequently a dazzling effect on other. users 5 of the road. This circumstance may be the cause of accidents and a certain uneasiness on the part of thedriver, so that careful automobiledrivers dare not fully utilize the possible speed of the vehicle.' I

In the ordinary used headlights the reflector consists of'a brightly polished paraboloid of rotation of metal with, nearlyin all cases, an electric source of light disposed at or near the focus of the paraboloid. With a paraboloid reflector with its source of light at the focus itis well known that all the light'received by the reflector will be reflected as a beam of rays parallel to the axis of rotation of the paraboloid, provided that the source of light be of such small bodily dimensions that it can be considered one single point. V Any source of light, however, is of appreciable size i. c. it extends outside of the mathe: matical axis of the paraboloid. Even if the centre of the source of light co -incide s with the focus, the rays of light will therefore not leave the reflector as a bundle of solely paral-v lel rays, but rays will also be emitted in many variousdirections and, especially, not only in downward direction, which'rays will not have any dazzling effect on the opposing traffie, but also in upward direction. Just these ascending rays are the ones that form a great nuisance on the roads, and preferably should be avoided entirely. I v The presentinvention solves this problem of dazzling, and is accurately. described and defined in the following. In order to understand the invention it is necessary, however, first to set forth a complete statement of the path of the rays under various conditions in and from a paraboloid reflector, and the following explanation is' 4.5 such a statement and is based upon a concise descriptive-geoinetrical research of the condi t'io-ns at hand. o I 1 1 The drawings illustrate a portion of this research. 7 i

Figs. 1, 3, 5,7, 9 and 11 show vertical axial sections of various paraboloid reflectors, Figs. 2, 4, 6, 8 and 12 show corresponding views in the direction of the-axis of the paraboloid, and

' Figs. 10 an -d 13 show other details. I V The following descriptive-geometrical re searches are based upon the assumption that there is provided, in a paraboloid reflector and at a certaindistance from the focus thereof, a light-emitting-circular disc without thick 6 ness and having its centre situated in the axis of'the paraboloid and'its plane perpendicular to the said axis. In Fig. 1 the disc is'shown as alineMN, intersecting the reflector axis at a point F and the distance from the focus F to the disc is marked d. An arbitrary circle onthe paraboloid is shown as a "line P;

P and the angle between radius vector'from the focus F to-the point P and the axis X of the paraboloid is marked 7 r As it is well known a ray of light emitted from a point and hitting a point of a reflecting plane will be reflected from this plane along a straight line determined by the last mentioned point and themirrorimage ofthe first mentioned point; If the reflecting sur- 7 face is curved, the tangential plane to the,

latter at the point hit by theray of. light re places the above mentioned reflecting plane.

' The tangent plane to an arbitrary I point P Fig. 1, in the. vertical axial plane of the V paraboloid is depicted, in ordinary rectangu V lar projection, as the'tange'nt T P to the point P The tangent plane, which 'is perpendicular to the axial plane (the XZ-plane, 5 where Z is the directrix of the parabola) is I considered to be reflecting. The mirror irnage of the plane F Q 'of the mirror'image' of. the light-emitting disc MNis shown as a line f Q andthe three planes, viz the plane 9o F Q of the luminous disc F Q the tangent plane T 1 to the point P and the plane of the mirror image of the luminous disc, are all passing through the line which is depicted as the point Q and is perpendicular to the XZ-plane.

A point f of the generatrix of the diametral parabola (the Z-axis) is the mirror image of the focus F. The point f is mirror image of the centre F of the luminous disc MN, and the mirror imageof the latter'is a. circle depicted as a line m n in the plane f Q and with its centre at f The line T f is the mirror image of the piece T F of the axis of the paraboloid, and the piece of line is the mirror image of the piece of line FF Z. The line P f, which is parallel to the axis of the paraboloid is the mirror image of radius vector Fl? to the point P and the point of intersection u between the line P f and the plane mQ of the mirror image oft-he luminous disc is the mirror image of the point of intersection U between the plane F Q of the disc MN and radius vector FP to the point P Fig. 2- shows, corresponding to Fig. l, a projection on a plane perpendicular to the X-axis and passing through the Z-axis, i. e. in the ZY plane, of the circle P P and the luminous disc MN as well as the mirror image of the latter, which image is shaped as an ellipse whose axis major is parallel to the Y-axis and is the mirror image of the horizontal diameter of the luminous disc projection of the line of intersection between the plane of the luminous disc and the planeof the mirror image of the same, and is tangent to a circle with centre at O and with radius OQ F Q in Fig. 1. Each point in the plane of the luminous disc corresponds to a point of the mirror imagethereof, and vice versa. To each line passing through the point a, in the plane ofrthe mirror image corresponds a line passing through the point U and situated in the plane of the disc, Figs. 1 and 2, and any two of these corresponding lines will intersect one another in the line of intersection 9 of the said two planes.

The rays of light emitted from the disc MN, Fig. 1, and reflected from the point P will after the reflection be directed as if they were emitted from the circular mirror image m n of the disc, Fig} 1, and they will form a cone the vertex of which is P and the 'generatrix' of which is the circle m n. The

outline of this cone is indicated in Fig. 1, viz. the triangle P m n.

In order to examine how the conditions will be for an arbitrary point 13 situated on the same circle of the paraboloid as the point P I may rotate this point together with its tangent plane etc. through an angle 9 about the'X-axis, so that the point P co-incides with the point B The tangentplane to P the ellipse E shown in Fig. 2. The entire thing will be congruent to what is shown for the point P the line OP f Fig. 2, being merely replaced by the line 013 0, which forms the angle 9 with the Z-axis. The rays of light emitted from the luminous disc and reflected from the point B of the paraboloid will form a cone the vertex of which is E and the directrix of which is the mirror image of the luminous disc projected as the ellipse E. /Vhen now a horizontal plane is laid through the point B this plane will intersect the mirror image of the luminous disc along a line 0 u g, which is parallel to the Y-axis and divide the ellipse E into two parts, an upper one and a lower one, and which similarly divides the conical bundle of reflected rays of lightinto two parts. Out of these rays the ones starting from the part of the mirror image situated above the line 0 u Q will be sloping downward and, consequently, not have any dazzling effect, while the rays of light startingfrom the part of the mirror image situated below this line will all be directed upward and, consequently, be dazzling. The rays of light starting from the horizontal line of intersection itself will be situated in the horizontal plane through the point B and will form the transition from the dazzling to the non-dazzling rays of light. In Fig. 2 the dazzling part of the mirror image is crosshatched, and will be seen immedately to correspond to the cross-hatched part of the luminous disc, which is determined by the line gUC,whose mirror image is the line 0 u g, as the line Qq, which is tangent, at the point Q, to a circle thece'ntre of which is the point 0 and the radius of which is 0Q=F Q in Fig. 1, is the line of intersection between the plane of the luminous disc and the plane of the mirror imagev ofthe' latter, and the point 0 of the axis major of the ellipse is the mirror image of the point C on the diameter of the luminous disc perpendicular to the line OB. The mirror image of the point U is u, the projection of which onthe YZ-plane co-in cides with the point 13,, since the line 13 is parallel to the X-axis'. The luminous disc is consequently divided, by the line UC, into two parts, one of which is cross-hatched and the other one is not cross-hatched, and a ray of light starting from the part of the disc that is not cross hatched will after. the reflection from the point 13 be directed downward and consequently not be dazzling, while any point of the cross-hatched part of the luminous disc will emit rays of light having after reflection fromB an upward direction and,

consequently, a dazzling effect. The rays of of the paraboloid be situated in the horizontal plane through this point and will form the transition between the dazzling and the non-dazzling rays of light. a

The 'line UC, which corresponds to the moving point B is determined in the follow ing manner, as it will now be understood from the above explan'ationlVith the point 0 as the centre two circles are drawn, viz. one with a radius equal to an=0U=0U =F U in'Fig. 1 and the other one with a radius equal to I) 0B 0B =P f in Fig. 2. Fig. 1 shows that a=cl tg and as Fig. 1, is equal to d, we have b=0lsin where t is the anglebetween the axis of the the circle P P on the paraboloid.

From the arbitrary point B on the circle P P the diameter 013 is drawn which paraboloid and radius vector to any point of intersects the said two circles with radius a and b, respectively, at point U and B on either side of the common centre 0. The line 0C is drawn at right angles to the diameter B B and from the point B a line is drawn, which is parallel to the Y-axis, and the point of intersection of which with the line OC determines the point C and, thereby, also the line CU. The two triangles 0013 and OCB are congruent, since their sides are mutually parallel and of equal length.

Allowing now the point B to move through the part of the circle P 1 that is situated above the XY-plane, the-various lines CU will generate. an envelope J for these lines as shown in Fig. 2. As a natural consequence of the manner of generation this curve is symmetrical with respect to the Z axis as well as with respect to'the Y-axis, but is only shown above the last mentioned axis. The curve has two cusps situated on the Y-axis, and the latter istangent to the curve at both of these points. If aline is drawn passing through the point of intersection D of the line CU and the Y-axis and being parallel tothe line BB iqe. perpendicular to the line 0G,:then the said line will intersect the line DC at a point H,and by the use of equiangular triangles we find:

2e Q1? 0U OU BU a +b Since OU is equal to a, we have now:

U on the Y-axis. For

point CO will co-incide with the Y-axis, which is common tangent to the two cusps of the curve situated on the Y-axis.

The point D is seen to co-incide with a cusp, and as simultaneously II will co-incide with O, the distance of the cusp from 0' will be-equalto a-b lm bl 1 By insertion of the values of a, and b we find: v

All the various lines UC are tangents. to

the envelope, and the point of contact be tween the curve and each individual tangent, i. e. the running pointof the curve, can be determined by geometrical construction.

'From Fig. 2 as well as from theabove explanation it follows that this curve is of importance in so far as rays of light emitted from any point of the portion'of the plane of the luminous disc that is situated above .lUL

sessing the property that rays of .light-starting there-from, afterreflection from any point in thelower halfofthe circle P 1 will all'be sloping downward. The lower semi iircle, is therefore left out of consideration .ere. I

Allowing nowthe entire plane P 1 and, I

consequently,the considered reflecting semivertex T of the paraboloid, then the angle g5 and, thereby, alsoa=altgj and b=cZ-sin 5 will increase. The vertex U of the curve J will therefore. move upward, and when we have a co, i.'8.'tl18 envelope will have its vertex U infinitely remote in the direction of the Z-axis, and the said envelope will therefore be of parabolic shape as appearing fromFig. 4, cf. Fig. 3. The curve consists of two separate branches, and the two cusps of the curve on the Y-axisywill be situated at the points of intersection between the said axis and a circle with radius 6 15, since circle on theparaboloid to move towards the If the plane P P, is moved further 'on to the part of the paraboloid situated inside of (behind) the plane passing through the focus F, for instance to the semi-circle through a point P Fig 5, then the curve will change into hyperbolic shape, Fig. 6, the point U being now situated on the same side of the centre as B, so that a (if-fig will be negative. The. curve will then assume the shape shown in Fig. 6 with asymptotes, the position of which may be determined by geometrical means. They are, however, irrevelant to the present invention. The two cusps of the curve which are situated on the Y-axis have their distance from the initial pont 0 determined by The branch of the hyperbolic curve situated in the second quadrant corresponds to the lower part of the part of the closed envelope that is situated in the second quadrant and shown in Fig. 2, while the branch of the i curve situated in the forth quadrant and exthe said distance being equal to d 26g which for =7r becomes 00 The curve corresponding to each individual value of e and, thereby, also to the non-dazzling part of the plane of the luminous disc situated inside of this curve will constantly and uniformly increase in size, each subsequent curve being always sit- V uated entirely outside the preceding one until the hyperbolic curve for 7r is reduced to and co-incides with the line of intersection between the plane of the luminous disc and the XY-plane, which means that the nondazzling part of the plane of the luminous disc here includes the entire half of the plane situated above the XY-plane.

If P P indicates the front edge of the paraboloid, i. e. the limiting circle of the reflector, the above explanation will show that if the luminous circle is limited to the portion of the plane F Q that is situated above the XY-plane and, at the same time, inside of the closed curve corresponding to the plane P 1 and, consequently to the angle ()5, see Fig. 2, then none of the rays emitted from the disc, when reflected from the upper half of the paraboloid, will be directed upward, and

they will therefore not have any dazzling efi'ect.

From the manner of generation of the curve it becomes evident that while the angle.

5 determines the type and shape of the curve (closed, parabolic or hyperbolic), the linear:

directly proportional to d, as the determining dimensions in this respect, viz. a=0ltg q& and Z =cZ-sin qS will both be directly proportional to d.

All curves with the same value of qS will therefore be similar, and if d is allowed to vary, while b is constant, the dimensions of the curve corresponding to each individual value of d willbe directly proportional to cl, and all these curves will be situated on one and the same cone surface, the vertex of which is at the focus and the directrix of which is one of the curves.

The above description shows that rays of light emitted from an arbitrary point situated above the horizontal plane through the axis of the paraboloid and also inside of a cone surface the vertex of which is the focus and the generatrix of which is one of the'mutually similar curves corresponding to the angle for instance thecurve which is situ ated in the boundary plane of the paraboloid and forms'the opening of the same and is shown in Fig. 8, by reflection from an arbitrary point of the upper half of the paraboloid will all be sloping downward and, consequently, cannot have any dazzling eflect. is the angle between the axis of the paraboloid and radius vector to the circle bounding the reflector and formingthe opening of the reflector, see Fig. 7. 7

If now the luminous disc is placed behind the focus (at MN in Fig. 1) and, like the disc MN, at a distance d from the latter, then an analogous research will lead to exactly the same partsof the same curves situated above the horizontal plane, and will lead to entirely analogous results, provided that the lower half of the paraboloid be used instead of the upper half. This will be evident, with iufiicent clearness, by an inspection of Figs.

to y Y 7 Here too a cone surface is found, the vertex of which is the focus, and which is congruent to the above mentioned cone but facing in the opposite direction, i. e. from the focus inward towards the vertex of the paraboloid, see Fig. 7. In analogy with the results. found for the first mentioned cone surface we find here that rays of light emitted from an arbitrary point situated above the horizontal plane through the axis and, simultaneously, inside of the last mentioned cone surface, when reflected from any point of the lower half of the paraboloid, will all. be sloping downward and, consequently, have no dazzling effect.

The result of the researches made hereis V consequently ated in front of the focus and having the above indicated shape, and

(2) That the condition to be filled in order that the rays of light reflected from the lower half of the paraboloid shall similarly all be sloping downward, and, consequently, not be dazzling is that the source of light shall be situated above the horizontal plane through the axis of-the paraboloid and'also inside of the cone surface situated behind the, focus and having the similarly indicated shape, see Fig. 7

These two conditions are filled simultaneously by the combination of the following two arrangements, which combination forms the present invention, viz. that the paraboloid is divided by a horizontal plane passing through the axis thereof, and that the lower half is displaced a certain distance in forward direction, parallel to the axis, and

that the source of light is disposed above the horizontal plane through the axis of the paraboloid and, simultaneously, inside of the space R; situated between the two focal points (for the two paraboloid halves) and bounded by the said two cone surfaces together, after the said displacement, see Fig. 9.

The above mentioned curve, which is novel and heretofore unknown in mathematics may suitably be called the reflector curve in agreement with the reason for which this curve is found here. The rectangular coordinates of the curve with reference to a horizontal X-axis and a vertical Y-axis with the initial point situated in the paraboloid axis are:

2 d s1nd s1n0 (cos 6+ 1 9; sin 0+cos qS-cos 0 and 3 y d s1ncos 0 curve are found in the following manner.

the latter from the cent-re O is formed in the horizontal plane by a rhomb,

The point C is the point of intersection betweeen thetangents to the points of the b-circle situated on tl163X-SlXiS and the- Y-axis, respectively, and the Iineintersects the X-axis at one of the cusps of the curve. It is easilyseenthat the distanceiof Xaxis at D, and if a line .isdrawn through the centre 0 parallel to DU, the same will intersect the a-article at the points G and G determining the two double tangents to the curve that are parallel to the Y-axis. Their points of contact with the latter :are situated halfways between their points of intersection with the a-circle and the X -axis, respectively.

The above described space bounded by two cone surfaces is-shown, to a larger scale,in Fig. 10. The boundaries of the-sa d space is one diagonal FF of which has the length 20? equal to the distance betweenthe focal points of the two paraboloid halves, and the other diagonal AA of which has a length equalto or, when the values of a and b expressed by the angle e are inserted, v

points are therefore, as easily seen, equal to re. the angle between thetopmost cone generatrix FH (or. andthe common.

axis FF ofthe paraboloid halves. Theidistance a from. the topmost pointH of'thedirectrix to the horizontal plane is equal to The space thus exactly'determined by. the selected values of d: and d or of the dimensions a and 6 depending thereon.

If the value ofd the half'distance between 7,5 A circle with diameter UB intersects the thetwo focal points) is maintained constant and, simultaneously, the angle qS is allowed to increase, so that thereflector is shortened,

the available space for the luminous body will increase, because thereby the diagonal of the rhomb as well as the height a of the directrix will increase. 'At "the same time, however, the fraction of the total quantity of light reflected by the reflector, i'. e. the useful part of the quantity of light willdecrease at a correspondingrate;

i If the angle increases to the value g the The luminous bodyflwill have-atits disposal in,

a space bounded at bottom by the square and sliaped as shown in Fig. 13. By the said arrangement each reflector is limited to the position of the paraboloid situated behind the focus thereof, so that only 50% of the light emitted from the source of light will be utilized by reflection. On the other hand the great advantage will be attained that it will here be easier to place the source of light close to the focal points, because by this arrangement'the latter will not be situated at the vertex of a cone as in the case of the closed space in Figs. 9 and 10, but in a corner, none of the angles of which is smaller than seeFigs. 11to 13, which is of importance, as the portion of the luminous body nearest to the focal axis, halfways between the focal points F and F and otherwise determined by having forthe given distance cl'and angle respectively, half the distance between the focal points and the angle between the axis of the lower half paraboloid and radius vector to the circle forming the front-edge of the same 'half paraboloid, the running point of the said reflector curve in a rectangular system of co-ordinates with axes X and Y being determined by the expressions:

where 9 is varying from zero to in. I

In testimony whereof he, hereunto aflixes his signature.

DITLEV BERG.

points is the portion giving the strongest and, V i

at the same time, the most far-reaching light. The lower and the'upper half paraboloids do not have to be congruent.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is In headlights for automobiles other vehicles and the like, thecombination with a light source of a parabolic reflector formed by two half paraboloids of rotation with coincident axes and bounded by a common horizontal plane,the focus of the lower one of said half paraboloids being displaced somewhat in forward direction relatively to the focus of the upper one and in the direction of the axes, the light-emitting parts of said light source being disposed in such a manner that they will be situated above the said horizontal plane and also inside of two mutually opposed single cone surfaces having each for its vertex the focal point of the corresponding half paraboloid and having for their generatrices the following curves: for the cone surface with vertex at the rear focal point F the reflector curve situated in the plane perpendicular to the axis halfways between the focal points' F and F and being 7 otherwise determined by having for the given distance d and angle qb, respectively, half the distance between the focal points and the angle between the axis of the upper half paraboloid and radius vector to the clrcle forming thefront edge of the same half paraboloid, and for the cone surface withvertex at the front focal point F the reflector curve situated in the plane perpendicular to the 

